One well known technique for fabricating microelectric devices is described in U.S. Pat. No. 4,209,358 which issued on June 24, 1980 to DiLeo et al. which is assigned to the instant assignee and is incorporated by reference herein. In particular, that patent describes the bonding of a Light Emitting Diode (LED) die to the bottom of a small reflective, electrically conductive cap using an unfilled epoxy adhesive. Once the die is bonded within the cup additional wet adhesive is placed on the top portion of the die and an electrically conductive lead is placed in contact therewith to provide an electrical connection thereto. Typically a thin metal rod is dipped into the wet adhesive to form a small pool or droplet of adhesive on the end thereof which is then placed in contact with the bottom of the cup to place the droplet therein.
A hollow hypodermic-type needle is then placed in contact with the die and a vacuum drawn to hold the die which is then lifted and placed in contact with the adhesive in the bottom of the cup. The vacuum is released, the needle withdrawn and additional adhesive deposited on the top of the die with a thin metal rod as previously described in relation to the depositing of adhesive in the bottom of the cup.
Heretofore the LED dies were miniature, but managable, e.g., a cube of about 0.015 inch or longer on each side. However, the dies are becoming smaller, e.g., approximately 0.011 inch square by 0.014 inch high. Such dies have been found to be most difficult to transfer using the vacuum-needle approach. The vacuum needles have such a small inside diameter (e.g., 0.007 inch) that they can become readily clogged with dirt or adhesive resulting in the die not being picked up or dropped during the transfer process which decreases the yield.
Accordingly, there is a need for an improved method of transferring and applying adhesive to the LED dice in which the transfer yields are substantially improved.